The phrase "in main" means primarily or mainly. The antonyms for this expression would be words such as subsidiary, secondary, or subordinate, which refer to things that are not the primary focus or most essential aspect of something. Other antonyms could include incidental, supplementary, or accessory, highlighting the fact that these things are not critical to the main idea or purpose. Using the appropriate antonym for "in main" in a sentence would depend on the context and the intended message. By identifying the antonyms of a word, we can expand our vocabulary and better communicate our ideas.